Eel is not a species of fish; it is an order of fish that consists of 19 families and approximately 800 species. The Common Eels (Anguilla Anguilla), are also known as fresh water eels. Its length is approximately 100 cm long and its weight is no heavier than 20 kg maximum. The skin colour of the eel can range from black, brown or olive green depending on which stage of life it is in. The common Eel has a fascinating life cycle; it breeds in the sea then migrates to freshwater to grow in order to spawn in the sea later in its life. The following report will describe in detail on 5 adaptations that enabled the Common Eel to survive until this very day. Scientific Classification
LEVEL
CLASSIFICATION
Kingdom
Animalia
Phylum
Chordata
Class
Actinopterygii
Order
Aguilliformes
Family
Aguillidae
Genus
Aguilla
Species
Aguilla Aguilla
Figure 1: Labelled Diagram of Common Eel
Habitat
Figure 2: The Sargasso Sea Source: http://upload.wikimedia.org/wikipedia/commons/8/8e/ Lines_of_sargassum_Sargasso_Sea.jpg
Common Eels have a long and complex life cycle; they live in both fresh water and salt water depending on the stage of life they are going through. They range in the European region from Western Europe to Britain. It is believed that all Common Eels spawn in the Sargasso Sea in winter or early spring. The larvae are slowly carried by the Gulf Stream for approximately three years until they reach the European coast. They then turn into a darker colour and migrate in large groups up the freshwater stream. These young eels grow in fresh water for 6 to 20 years (male: 6 to 12 years; female: 9 to 20 years). Eels can mature much faster in warmer waters.
During this time they become sexually mature and turn into a dark silvery colour. Eels are capable of surviving for a period out of water, they will cross damp meadows to reach new habitat. Because of this behaviour, eels became one of the most widely distributed fresh water fish in Europe and Britain. On a dark night, the adult eels migrate back to the sea and live in holes or mud on the seabed.
The Common Eel is a predator to small marine creatures like fish or shrimps. Even though eels have extremely poor eyesight, they have a very keen sense of smell used to detect its nearby preys. The eel will usually hide in a narrow gap between rocks to wait for its right chance to ambush its food.
Figure 3: Map of Sargasso Sea Source: http://www.ilike2learn.com/ilike2learn/seamaps/SargassoSea.jpg
One of eel’s most fearful predators is the shark or basically any carnivorous fish that are bigger than it. Another predator is actually us humans. Cooked eel has been a long traditional food in many countries in the world (grilled eel rice is a traditional food in Japan). Even though eel blood is highly toxic, cooking it completely will remove all the poison.
All fish have a slime covering their bodies; this slime is produce in the glands beneath their scales. Fish constantly pump water in and out of their gills in order to keep balance of the water inside their bodies and the water in the sea, this process is called osmoregulation. The thickness of the slime affects how much water a fish can take in and out, the thinner the more; the thicker the less. Some scientists believe that the slime on eels also assists them to migrate effortlessly from saltwater to freshwater and vice versa.
The slime on eels has the same function as our skin, it protects the fish by making is slippery. This mucous surface blocks pathogens and parasites from entering the fish’s body and protects any external wounds. It also allows the eel to slide easily through barriers. The thin layer of slime fills in the gap between the tiny scales; making the eel more streamline which reduces friction and allows it to escape faster from predators.
Structural TWO - Elongated Bodies
All eels have elongated bodies which resembles the appearance of a snake. The Common Eel’s long bodies are evolved according to their habitat; they allow the eels to hide in narrow caves and to lie on the seabed ready to attack their prey. With their thing bodies, they will be able to slide through rocks with no difficulty while camouflaging themselves.
Common Eels have different eating habits in different stages of their lives. Young eels that live in fresh water consume insect larvae, dead fish, and small crustaceans. Saltwater adult eels have a much wider food habit; they eat anything from fish to small mammals like a mouse. Adult Common Eels will essentially eat anything they can find, even dead organisms.
Behavioural ONE - Nocturnal
Figure 5: Nocturnal Eel Source: http://forums.sportdiver.com/videos/files/photos/44a2e0804995fafL.jpg
Many animals are nocturnal in the wild, meaning they are active at night. Being nocturnal allows the animal to avoid the heat of sun and other predators that are diurnal. Also, being nocturnal also provides an advantage for animals that hunt. The predator can conceal itself effortlessly from its prey and wait for the right chance to strike. The Common Eel is not an exception. It hides in between rocks and narrow gaps, waiting for its prey to come close enough for its lethal kill. Since eels are night hunters, they have extremely poor eyesight. Common Eels rely on their keen sense of smell to locate preys like fishes or shrimps.
Behavioural TWO - Hibernation
Some animals like the grizzly bear and squirrels hibernate in winter; it can help animals to survive the toughest conditions. By hibernating, an animal decreases its energy consumption to the lowest possible level. This is a process where animals lower their body temperatures and heart rates to preserve energy due to stress or rough conditions. Different animals have different ways to hibernate, the squirrel wakes up every couple of days to eat and get rid of body waste. The grizzly bear on the other hand, can stay dormant for up to 7 months without waking up at all. It is not unusual for a Common Eel to hibernate in the cold arctic winter. They tend to dig themselves into deep mud and stay dormant until spring. The eels curl up tightly and will produce a slime covering the entire body. However, hibernation does not occur to all Common Eels, some living in warmer waters will remain active throughout the winter.
Physiological ONE - Toxic Blood
All animals have features that either defend themselves or aid them to attack other animals. For example, a tortoise will retreat into its shell when danger approaches and wolves have a keen sense of smell assisting them to hun their prey. Animals need to be able to escale from predators in orfer to survive in this world. Common Eel blood is extremely toxic, it may cause muscles cramps, which can directly affect the heart. When its predator comes in contact with its toxic blood, it will numb them for a few seconds. These few seconds are longe nough for the eel to escape from its jaws. Eel's predators include larger carnivorous fish like shark or even humans. Only 0.1mL of eel's blood is strong enough to kill a small mammal like a rabbit. The toxin in eel's blood is discovered by Charles Robert Richet in 1913. However, the toxin in the blood can be removed completely by cooking the eel.
Ancient Animal - Enchelion Montium
Future Animal - Scaled Camouflaging Eel
Common Eel
Eel is not a species of fish; it is an order of fish that consists of 19 families and approximately 800 species. The Common Eels (Anguilla Anguilla), are also known as fresh water eels. Its length is approximately 100 cm long and its weight is no heavier than 20 kg maximum. The skin colour of the eel can range from black, brown or olive green depending on which stage of life it is in. The common Eel has a fascinating life cycle; it breeds in the sea then migrates to freshwater to grow in order to spawn in the sea later in its life. The following report will describe in detail on 5 adaptations that enabled the Common Eel to survive until this very day.
Scientific Classification
Habitat
Common Eels have a long and complex life cycle; they live in both fresh water and salt water depending on the stage of life they are going through. They range in the European region from Western Europe to Britain. It is believed that all Common Eels spawn in the Sargasso Sea in winter or early spring. The larvae are slowly carried by the Gulf Stream for approximately three years until they reach the European coast. They then turn into a darker colour and migrate in large groups up the freshwater stream. These young eels grow in fresh water for 6 to 20 years (male: 6 to 12 years; female: 9 to 20 years). Eels can mature much faster in warmer waters.
During this time they become sexually mature and turn into a dark silvery colour. Eels are capable of surviving for a period out of water, they will cross damp meadows to reach new habitat. Because of this behaviour, eels became one of the most widely distributed fresh water fish in Europe and Britain. On a dark night, the adult eels migrate back to the sea and live in holes or mud on the seabed.
The Common Eel is a predator to small marine creatures like fish or shrimps. Even though eels have extremely poor eyesight, they have a very keen sense of smell used to detect its nearby preys. The eel will usually hide in a narrow gap between rocks to wait for its right chance to ambush its food.
One of eel’s most fearful predators is the shark or basically any carnivorous fish that are bigger than it. Another predator is actually us humans. Cooked eel has been a long traditional food in many countries in the world (grilled eel rice is a traditional food in Japan). Even though eel blood is highly toxic, cooking it completely will remove all the poison.
Structural ONE - Slimy Surface
All fish have a slime covering their bodies; this slime is produce in the glands beneath their scales. Fish constantly pump water in and out of their gills in order to keep balance of the water inside their bodies and the water in the sea, this process is called osmoregulation. The thickness of the slime affects how much water a fish can take in and out, the thinner the more; the thicker the less. Some scientists believe that the slime on eels also assists them to migrate effortlessly from saltwater to freshwater and vice versa.
The slime on eels has the same function as our skin, it protects the fish by making is slippery. This mucous surface blocks pathogens and parasites from entering the fish’s body and protects any external wounds. It also allows the eel to slide easily through barriers. The thin layer of slime fills in the gap between the tiny scales; making the eel more streamline which reduces friction and allows it to escape faster from predators.
Structural TWO - Elongated Bodies
All eels have elongated bodies which resembles the appearance of a snake. The Common Eel’s long bodies are evolved according to their habitat; they allow the eels to hide in narrow caves and to lie on the seabed ready to attack their prey. With their thing bodies, they will be able to slide through rocks with no difficulty while camouflaging themselves.
Common Eels have different eating habits in different stages of their lives. Young eels that live in fresh water consume insect larvae, dead fish, and small crustaceans. Saltwater adult eels have a much wider food habit; they eat anything from fish to small mammals like a mouse. Adult Common Eels will essentially eat anything they can find, even dead organisms.
Behavioural ONE - Nocturnal
Many animals are nocturnal in the wild, meaning they are active at night. Being nocturnal allows the animal to avoid the heat of sun and other predators that are diurnal. Also, being nocturnal also provides an advantage for animals that hunt. The predator can conceal itself effortlessly from its prey and wait for the right chance to strike. The Common Eel is not an exception. It hides in between rocks and narrow gaps, waiting for its prey to come close enough for its lethal kill. Since eels are night hunters, they have extremely poor eyesight. Common Eels rely on their keen sense of smell to locate preys like fishes or shrimps.
Behavioural TWO - Hibernation
Some animals like the grizzly bear and squirrels hibernate in winter; it can help animals to survive the toughest conditions. By hibernating, an animal decreases its energy consumption to the lowest possible level. This is a process where animals lower their body temperatures and heart rates to preserve energy due to stress or rough conditions. Different animals have different ways to hibernate, the squirrel wakes up every couple of days to eat and get rid of body waste. The grizzly bear on the other hand, can stay dormant for up to 7 months without waking up at all. It is not unusual for a Common Eel to hibernate in the cold arctic winter. They tend to dig themselves into deep mud and stay dormant until spring. The eels curl up tightly and will produce a slime covering the entire body. However, hibernation does not occur to all Common Eels, some living in warmer waters will remain active throughout the winter.
Physiological ONE - Toxic Blood
All animals have features that either defend themselves or aid them to attack other animals. For example, a tortoise will retreat into its shell when danger approaches and wolves have a keen sense of smell assisting them to hun their prey. Animals need to be able to escale from predators in orfer to survive in this world. Common Eel blood is extremely toxic, it may cause muscles cramps, which can directly affect the heart. When its predator comes in contact with its toxic blood, it will numb them for a few seconds. These few seconds are longe nough for the eel to escape from its jaws. Eel's predators include larger carnivorous fish like shark or even humans. Only 0.1mL of eel's blood is strong enough to kill a small mammal like a rabbit. The toxin in eel's blood is discovered by Charles Robert Richet in 1913. However, the toxin in the blood can be removed completely by cooking the eel.
Bibliography
Aguilla Aguilla. Animal Diversity Web. (1995). Last Retrieved 19th July 2010. http://animaldiversity.ummz.umich.edu/site/accounts/pictures/Anguilla_anguilla.html
Common Eel – Aguilla Aguilla. MarLIN. (2010). Last Retrieved 19th July 2010.
http://www.marlin.ac.uk/speciesinformation.php?speciesID=2521
Common Eel. ARKIVE images of life on Earth. (2003). Last Retrieved 20th July 2010.
http://www.arkive.org/common-eel/anguilla-anguilla/info.html
Eel Fact Sheet. Yorkshire Wildlife Trust. (2010). Last Retrieved 20th July 2010.
http://www.ywt.org.uk/_filestore/File/Wildlife%20Factsheets/Eel%20Fact%20Sheet.pdf
Why are eels slippery?. How stuff works. (2008). Last Retrieved 20th July 2010.
http://animals.howstuffworks.com/fish/eels-slippery.htm/printable